05 LLY communication issues

rcashman

New member
Jun 7, 2023
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Idaho
What voltage do you have on the class 2 comm wires?
With the comb in the splice pack and the ign0 fuse in i have erratic voltage. 3 to 6.9 volts. When i pull the comb and jump the communication wire in the splice pack to the K wire it has a square wave on the O-scope but is much different looking than anyother module. Meaning the waves are more frequent. I have the scope set at 2v every 200ms i believe. Had to slow it down so i could see the waves.
 

2004LB7

Well-known member
Dec 15, 2010
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Norcal
I'm going to guess you got moisture or corrosion in the harness or connector somewhere. Something that is bleeding voltage from the ignition power onto the comm wires. You could isolate all the ignition power wires and ohm them to the comm wires and see if any have lower resistance. Even a few kohms is probably too low.
 

rcashman

New member
Jun 7, 2023
19
1
3
Idaho
I'm going to guess you got moisture or corrosion in the harness or connector somewhere. Something that is bleeding voltage from the ignition power onto the comm wires. You could isolate all the ignition power wires and ohm them to the comm wires and see if any have lower resistance. Even a few kohms is probably too low.

I'm going to guess you got moisture or corrosion in the harness or connector somewhere. Something that is bleeding voltage from the ignition power onto the comm wires. You could isolate all the ignition power wires and ohm them to the comm wires and see if any have lower resistance. Even a few kohms is probably too low.
Just want to make sure i understand. When you say isolate ignition from comm you mean opening the remaining harnesses apart.
Can i check continuity between the two? Would that tell me what i need to know?
 

2004LB7

Well-known member
Dec 15, 2010
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I mean separate the wires from each module or splice point. Should be able to just pull the connectors off each module to isolate them. Same for under the fuse box. When you pull all the connectors you should just have a wire running from one connector to the other. Then you can measure between the between the power and comm wires.

You need to use the process of elimination. Rule our one wire at a time. Then if all wires check out ok. Then plug one connector in and measures at the other end. You should see one wire or one connector where the readings are different or change. That's where you need to look
 

rcashman

New member
Jun 7, 2023
19
1
3
Idaho
I mean separate the wires from each module or splice point. Should be able to just pull the connectors off each module to isolate them. Same for under the fuse box. When you pull all the connectors you should just have a wire running from one connector to the other. Then you can measure between the between the power and comm wires.

You need to use the process of elimination. Rule our one wire at a time. Then if all wires check out ok. Then plug one connector in and measures at the other end. You should see one wire or one connector where the readings are different or change. That's where you need to look
Well that sounds like no fun at all.
I mean separate the wires from each module or splice point. Should be able to just pull the connectors off each module to isolate them. Same for under the fuse box. When you pull all the connectors you should just have a wire running from one connector to the other. Then you can measure between the between the power and comm wires.

You need to use the process of elimination. Rule our one wire at a time. Then if all wires check out ok. Then plug one connector in and measures at the other end. You should see one wire or one connector where the readings are different or change. That's where you need to look
Sounds good. I'm going to get back at it late Thursday.
Thanks.
 
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